The preparation of butynediol by the reaction of formaldehyde and acetylene, the subsequent hydrogenation of the butynediol to form crude 1,4-butanediol and the distillation of butanediol are described in U.S. Pat. No. 4,371,723.
Preparation of "very pure" 1,4-butanediol by fractional distillation of a water-free stream is described in U.S. Pat. No. 3,891,511.
When crude 1,4-butanediol is conventionally prepared from the starting materials, formaldehyde and acetylene using buffered reaction conditions, the resulting stream contains high boiling organic compounds, including color forming materials, precursors of color and tar formers, inorganic salts and organic salts including sodium formate that if not removed eventually from the BDO, give a product that is not suitable for high-volume, color sensitive end uses such as the formation of polyester, polyurethane and in the preparation of tetrahydrofuran. These high boiling compounds and salts, if not removed early in the purification process react with themselves and with BDO which produces tars and color formers; thus reducing the yield of BDO and reducing its utility. These wastes are economically undesirable, and are pollutants that pose difficult disposal problems.
Now it has been found that these impurities (high boilers including color forming materials and their precursors and precursors of tar, organic and inorganic salts) present in the crude BDO, can be removed very efficiently at very high yield by subjecting the crude BDO to distillation under mild conditions wherein the amount of these impurities is reduced to not more than 0.1% by weight based on the total organics. The purified concentrated BDO can be further distilled to remove water, low boilers and remaining high boilers to provide a BDO product for use in the color sensitive end uses, e.g., polyester, etc., or the purified concentrated BDO can be used to form a high purity colorless tetrahydrofuran. It has also been found that the yield from crude BDO to refined BDO and yield from crude BDO to tetrahydrofuran is greatly increased and that the purity of the finished product BDO and tetrahydrofuran is very high. An additional important feature of this invention resides in the fact that wastes can be minimized at the source.